API params in Java

Hi,
I'm writing a web service client in Java and trying to add e.g. function:
mail_domain_add(...)
What should be a type of params? When I use mail_domain_get I get HashMap as return and everything is fine. When I try to use HashMap or LinkedHashMap as type of params everything looks fine as well. I get the mail_domain_id but all params (server_id, domain, active) are not set. As a result I add new mail domain but params values are empty.

OK, I know already what was wrong but I still don't know exactly why. If any of you use web service generation in Eclipse with Axis, one should make changes in class <webservice_name>SOAPStub.java in constructor. Your QName should be different to QName used as a param and you should add lines:
java.lang.Class mapsf = org.apache.axis.encoding.ser.MapSerializerFactory.class;
java.lang.Class mapdf = org.apache.axis.encoding.ser.MapDeserializerFactory.class;
with no need to use is further. If any of you can explain me what exactly happens then, I would be pleased